Building Custom Headers Help

[gt500biatch]

hey guys, I'm getting some custom headers made up (tuned length) with mandrel bend and exhaust (with hi flow cat etc)

 

i just need some help in what size tubing i need and the thickness ? they will be 4-1 headers, however I'm unsure to what size/thickness to get for max performance.

 

this is what my build is 4age 20v

 

toda over sized high compression forged pistions C/R 12:5:1

H beam forged condrods

ARP head studs

ARP crank studs

Kelford 194-C racing cams

Toda racing adj. cam gears

Full head reco port and polish

Supertech 1mm over size valves

Supertech racing vavle springs

Tomei crank caps

TRD 0.8mm multi layer metal head gasket

TODA timeing belt

1zze Coilpacks

ITB'S (trumpets)

 

thanks :)

Edited September 3, 2014 by gt500biatch

[snot35]

Any reason for custom headers over something commercial?

[gt500biatch]

iv done a fair bit of research, most headers that are cheap have a fair few shitty reviews, if I'm going to spend the money i might as well do it right. I'm currently running those shitty trd copy ones. most proper tuned length ones cost over 1k anyway so might as well get them built ?

[LittleRedSpirit]

Exactly. Go see RIck Sendall and have something like these made for half the price of toda R.

 

 

Make sure you tell him to connect 1-4 and 2-3 in the first phase. Darn v8 guys don't know Toyota firing order as I discovered /\/\

 

As far as pipe sizes, with primaries I think one size bigger than your exhaust port is always good as it creates a reversion ledge and helps stop pressure waves going back from that point and hurting your flow. The scondaries are a point of debate, and quite honestly, if anybody posts here and tells you this stuff, they probably don't know shit, they are basically giving away trade secrets they don't know. I trusted Ricks choice on size, and I think he has done a good job. He asked me what CR, where the peak power was made, and engine volume and then did his planning from that. There is a relationship between the aperture in the last collectpr and the pipe size, get it wrong and you lose much power.

[snot35]

That's sort of why I asked. If you're getting headers made, then it's curious to ask for tube sizing, I would have thought the maker would be able to help with that, or you're leaning toward a shot in the dark which is probably the same as getting something off the shelf :) There's a fair art to proper headers, is my understanding.

[gt500biatch]

personal preference.. ill be going for 4-1 rather than 4-2-1 so i don't need to worry about 1-3 & 4-1 being connected. however some say 2.5" tubing down to a 2.5" cat then 2.25" the rest of the way. and the tube length at 28"

 

does that sound good ? @littlered could you measure yours (length) and give me a rough idea how long yours are ?

[LittleRedSpirit]

Its not going to translate exactly mate. Mine are on a 2.4 engine that will rev only to six grand and be 11:1 compression eventually, when I get around to fitting my forged slugs.

 

Its pretty long to the lower collector, I think longer systems in general give you smoother power. I wouldnt bother with the pipe reduction after the cat or resonator, just go the one size all the way through.

 

Your engine is desgined to sit wide open, so why restrict anything. I personally think there is something in it that Toyota equips almost all their engines with 4-2-1 if they are under 2 litres. Even a stock 20v, and having had each to play with, I prefered the 421 all day! Way fatter midrange for sure, even when they were cracked and rooted the 4-2-1s still gave me better performance than the new kaizen trd copies I put on after, even with port matching and polishing a bit in the collector, which I never did on the 4-2-1s. All the tidying up did was lessen the reversion moment you get around 4000 revs in a 20v.

 

Giive me a ring and Ill give you Ricks digits. He is back working from home now and pumping it out. He is not far from you, he is at Runcorn on Beenleigh road near Balaclava St intersection. You don't have to use him, but have a chat with him, and go there and have a look at some of the things he is working on, its quite illuminating.

 

 

Edited September 4, 2014 by LittleRedSpirit

[oldeskewltoy]

What chassis is this 20V going into?

 

What diameter are the exhaust ports?

 

I'd shoot for the exhaust port diameter, and then add 4mm to 6mm, and that should be your ID target for the pipe. As far as length, 28" corresponds to more of a street engine, for a worked 20V, I'd think your target length will be closer to 26"

Edited September 5, 2014 by oldeskewltoy

[filfrederick]

I would also push for a megaphone with a reverse cone after the collector, it helps with the reverb pulses for scavenging.

here is what i am talking about.

[filfrederick]

and make sure they are a proper merge style collector, not the shitty exhaust shop press-bent style.

are you wanting stainless? they need a whole different design to stop them from cracking down the line, slip joins and such.

[gt500biatch]

thanks for the info guys, ill be getting them made at the coast, and yeh it wont be done dodgy exhaust shop press style, I'm unsure about my exhaust ports will have to measure them

 

and its in a ke70 bud :)

 

and i was thinking of going mild steel to avoid cracking

[LittleRedSpirit]

Mild steel gives a way less gay sound on a 20v, a lot fatter and less raspy. Stainless pipes sound awful mostly. That darn zingy jap noise, Id prefer a little burble down low. I liked the sound of mine.

 

Edited September 7, 2014 by LittleRedSpirit

[gt500biatch]

what design /measurements for the reverse cone bro ?

[gt500biatch]

size/length/taper

[LittleRedSpirit]

The good fabricators wont even tell you. Youd have to trial and error to work out the optimum. The beauty is that you get somethig totally unique and have a shot at getting it freakily correct and having some particularly individual sound and power delivery, as opposed to the same shit as everybody else with the same exact results.